1. Field of the Invention
The present invention relates to a method and device for assisting a driver of a vehicle to avoid collisions with obstacles.
2. Description of Related Art
The increasing presence of electrically controllable braking and steering devices in motor vehicles, and of sensors that sense possible obstacles in the vehicle's surroundings, makes possible systems for avoiding and/or reducing the consequences of collisions with obstacles.
With the aid of surroundings-sensing systems, for example, it is possible to detect potential collisions with obstacles at an early stage. Such accidents can be avoided by timely warning of the driver or by influencing the vehicle's motion by way of controllable braking and steering devices. In critical situations, moreover, the braking system can be prepared for emergency braking or the restraint system can be prepared for an accident.
Among the sensors for sensing the vehicle's surroundings are, for example, ultrasonic, radar, lidar, and/or video systems. Available as controllable subsystems of braking systems for active pressure application are, for example, hydraulic units of ESP systems, actively controllable braking force intensifiers, electrohydraulic braking systems, or future electromechanical braking systems. Active steering systems or steer-by-wire (SBW) systems are possibilities for influencing steering.
Published German patent document DE 101 18 707 describes the carrying out of preparatory actions, in a context of a collision risk, that have no vehicle-decelerating effect but do prepare for vehicle deceleration.
Warning devices for collision avoidance have also been described, which are not aimed at assisting the driver in carrying out an evasive maneuver.
Systems for collision avoidance or collision consequence reduction intervene in the system by way of an active braking and/or steering intervention. The intensity of the braking interventions is, however, not optimized for assisting an evasive maneuver. For example, published European patent documents EP 1 300 275 and EP 0 891 903 describe a device that automatically brakes a vehicle at exactly the time when the latter, exploiting the limit of driving physics, can no longer avoid a collision with an obstacle. The individual escalation steps, with the associated interventions that ultimately lead to triggering of the system, are noted in published German patent document DE 102 20 567. For automatically guided vehicles, systems for evasion and for collision avoidance are described in published German patent document DE 38 30 790, published European patent document EP 0 433 322, or published international patent document WO 90 02985; for non-automatically guided vehicles, such systems are indicated in published international patent document WO 02 08010 and published German patent document DE 198 31 071, the latter not acting fully automatically but instead proposing the evasion trajectory to the driver by way of a steering torque.
Vehicle dynamics control method are also described which, however, have only the purpose of optimally implementing the driver's steering input. These devices do not, however, possess a surroundings sensor suite, but only a vehicle-related sensor suite. The braking interventions are therefore not capable of being adapted to the location of obstacles, but have only the purpose of stabilizing the vehicle operating state.
In addition, German Patent Application DE 10 2004 008894 of Feb. 24, 2004 describes a system that can assist an evasive maneuver by way of suitable haptic steering inputs. Simultaneous braking of the vehicle to optimize the evasion trajectory is not addressed.